The invention relates to a method for blow molding containers, wherein a preform is deformed after thermal conditioning within a blow mold, arranged in the area of a blow molding station, by the influence of blow molding pressure in the container, and wherein a blow molding gas is conducted through a connecting element into the interior of the preform and wherein, after blow molding, a rinsing gas is conducted through the interior of the container, and wherein a plurality of blow molding stations are used.
Moreover, the invention relates to a device for blow molding containers which includes at least two blow molding stations which each have at least one blow mold, and in which a flow path for a blow molding gas for blow molding the containers extends through a connecting element, and in which the blow molding stations are connected to a device for supplying a rinsing gas.
When the containers are formed by the influence of blow molding pressure, preforms of a thermoplastic material, for example, preforms of PET (polyethlene terephthalate), are fed within a blow molding machine to different processing stations. Typically, such a blow molding machine includes a heating device, as well as a blow molding device in whose area the previously thermally conditioned preform is expanded into a container by biaxial orientation. The expansion takes place by means of compressed air which is conducted into the preform to be expanded. The sequence in such an expansion of the preform is explained in DE-OS 43 40 291 with respect to method technology. The introduction of the pressurized gas mentioned in the beginning also includes the introduction of compressed gas into the developing container bubble, as well as the introduction of compressed gas into the preform at the beginning of the blow molding process.
The basic construction of a blow molding station for the container deformation is described in DE-OS 42 12 583. Possibilities for thermally conditioning the preforms are explained in DE-OS 23 52 926.
The preforms, as well as the blow molded containers, can be transported within the device for blow molding by means of different manipulating devices. The use of transporting mandrels on which the preforms are placed has been found particularly useful. However, the preforms can also be manipulated with other support devices. The use of gripping tongs for manipulating preforms and the use of expanding mandrels, which can be inserted for support in an area of the opening of the preform, are also among the available constructions.
A manipulation of containers using transfer wheels is described, for example, in DE-OS 199 06 438, in an arrangement of the transfer wheel between a blow molding wheel and a delivery section.
The manipulation of preforms already mentioned above takes place, on the one hand, in the so-called two-stage method, in which the preforms are initially manufactured by an injection molding process, are subsequently intermediately stored and are only later conditioned with respect to their temperature and blown into a container. On the other hand, the manipulation takes place in the so-called single-stage methods in which the preforms are suitably thermally conditioned an subsequently blown up, immediately following their production by means of injection molding and a sufficient solidification.
With respect to the blow molding stations used, various embodiments are known in the art. In blow molding stations which are mounted on rotating transport wheels, a book-like opening of the mold carriers can be frequently found. However, it is also possible to use mold carriers which are slidable relative to each other, or are guided in some other manner. In stationary blow molding stations, particularly those suitable for accommodating several cavities for the formation of containers, typically plates that extend parallel to each other are used as mold carriers.
Particularly in the manufacture of containers which are intended for having hot liquids filled into the, blow molds are used which have a temperature above an ambient temperature. These hot blow molds have the result that solidification of the material of the blow molded containers takes place only relatively slowly. Therefore, after carrying out the blow molding process, in such manufacturing methods frequently a rinsing gas is introduced into the container which causes cooling of the container walls, and thereby reinforces a faster removal of the finished containers out of the blow mold.
Such a rinsing air can be supplied, for example, through a hollow stretching rod which is provided with corresponding discharge openings. However, basically other variations for supplying the rinsing gas are possible. For controlling the supply of rinsing gas, usually special lines and valve circuits are used. Moreover, frequently a pressure level is predetermined for the rinsing gas which neither corresponds to a conventional low preliminary blowing pressure, nor to a higher principal blowing pressure. Consequently, the corresponding pressure level has to be made available separately through pressure regulators or additionally separately from the other pressures. Consequently, compared to a standard machine, the supply of the rinsing gas requires significant modifications with respect to device technology, or complete control units which are specialized for the respective application must be made available.